将背景颜色更改为黑色，则需要修改ThemeData中scaffoldBackgroundColor的backgroundColor属性。你可以这样做：

class MyApp extends StatelessWidget {
  const MyApp({Key? key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      theme: ThemeData.dark().copyWith(
        scaffoldBackgroundColor: Colors.black, // Change background color to black
      ),
      title: "Test",
      home: Scaffold(body: Center(child: Text("Test"))),
    );
  }
}

你正在做的是设置应用程序的配色方案。要更改整个应用程序的背景颜色，您需要编写如下代码。

@override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(
        scaffoldBackgroundColor: const  Color(0xFF000000),
        colorScheme: const ColorScheme.dark().copyWith( background: const Color(0xFF000000)),
      ),
      title: 'Button Types',
      home: const Scaffold(
        body: ButtonTypesExample(),
      ),
    );
  }